232 Contributions to Electricity and Magnetism. 
SECTION VI. 
The production of Induced Currents of the Different Orders 
from Ordinary Electricity. 
98. Dr. Faraday, in the ninth series of his researches, remarks, 
that “the effect produced at the commencement and the end of 
a current (which are separated by an interval of time when that 
current is supplied from a voltaic apparatus) must occur at the 
same moment when a common electrical discharge is passed 
through a long wire. Whether if it happen accurately at the 
same moment, they would entirely neutralize each other, or 
whether they would not still give some definite peculiarity to the 
discharge, is a raatter remaining to be examined.” 
99. The discovery of the fact that the secondary current, 
which exists but for a moment, could induce another current of 
considerable energy, gave some indication that similar effects 
might be produced by a discharge of ordinary electricity, provided 
a sufficiently perfect insulation could be obtained. 
Fig. 11. 
iO LVM ivi 
O00 
a glass cylinder, b Leyden jar, ¢ magnetizing spiral. 
100, To test this, a hollow glass cylinder, Fig. 11, of about 
six inches in diameter, was prepared with a narrow riband of tin 
foil, about thirty feet long, pasted spirally around the outside, and 
a similar riband of the same length, pasted on the inside ; 80 that 
the corresponding spires of the two were directly opposite each 
other. The ends of the inner spiral passed out of the cylinder 
through a glass tube, to prevent all direct communication betwee? 
the two, When the ends of the inner riband were joined by the 
magnetizing spiral (11,) containing a needle, and a discharge from 
a half gallon jar sent through the outer riband, the needle ws 
